The present invention relates to a method of manufacture and a device for the manufacture of a liquid crystal display device which impart optical anisotropy in a fixed direction to a surface of an orientation film formed of an organic polymer film or the like that is applied to a substrate by irradiating polarized light to a surface of the organic polymer film or the like.
As an example of a device which displays various images which contain still images or moving images, a liquid crystal display device has been popularly used. This type of liquid crystal display device basically includes a liquid crystal panel in which a liquid crystal layer is sandwiched between two substrates, wherein one substrate is made of transparent glass or the like. The liquid crystal panel is classified into a type in which given pixels are turned on and off by selectively applying voltages to various electrodes in pixels which are formed in a matrix array on the substrate of the liquid crystal panel and a type in which various electrodes forming pixels and active elements for selecting pixels are formed in a matrix array on the substrate of the liquid crystal panel, and the turning on and off of given pixels is effected by selecting the active elements. Particularly, the latter-type liquid crystal display device is referred to as an active matrix type liquid crystal display device, and it constitutes the most widely used liquid crystal display device in view of its excellent contrast performance, rapid display performance and the like.
The conventional active matrix type liquid crystal display device, depending on the difference in the method for controlling the orientation direction of the liquid crystal, is classified into a liquid crystal display device adopting a so-called vertical electric field method (also referred to as a TN method) in which the orientation direction of liquid crystal is controlled by generating an electric field by applying a voltage between pixel electrodes formed on one of two substrates and counter electrodes formed on another substrate, and a liquid crystal display device adopting a so-called lateral electric field method (also referred to as an IPS method) in which pixel electrodes and counter electrodes are formed on one of two substrates and the orientation direction of liquid crystal is controlled by forming an electric field in a direction substantially parallel to a surface of the substrate by applying voltages between the pixel electrodes and the counter electrodes.
As a typical example of the method which aligns liquid crystal molecules which constitute a liquid crystal layer in a given direction, an organic orientation film having the following constitution has been used. That is, the organic orientation film is constituted of an organic high molecular thin film, such as a polyimide-based film formed on the substrate, and a liquid crystal orientation control performance is imparted to the film by applying rubbing treatment to the film. Further, there also is a known technique which is referred to as optical orientation. In this technique, an orientation film which is formed of an organic high molecular thin film made of polyimide resin or the like is formed on a substrate, and a liquid crystal orientation control performance is imparted to the orientation film by the irradiation of light to the orientation film (for example, see U.S. Pat. No. 4,974,941 (literature 1), Japanese Patent Laid-Open No.34699/1993(literature 2), Japanese Patent Laid-Open No.281937/1994(literature 3), Japanese Patent Laid-Open No.247319/1995(literature 4).
Further, particularly, in the TN method, in addition to imparting of an orientation control performance to the orientation film, it is necessary to impart a so-called pretilt angle which causes the orientation axis of the liquid crystal molecules in a non-driven state to be tilted with respect to a surface of the substrate by a given angle. In the optical orientation technique which has been proposed conventionally, in general, first of all, when an orientation control performance is to be imparted to an orientation film, an optical orientation material is applied to the surface of a substrate, and a polarized light obtained by performing polarization treatment on a light flux from a light source using a first device is irradiated to the orientation film. Thereafter, using a second device in which a surface of the orientation film (the surface of the substrate) and the polarized light irradiating direction is arranged at an angle corresponding to the above-mentioned pretilt angle, polarized light is irradiated to the orientation film to impart a pretilt angle to the orientation film. Here, as an example of literature which discloses the related art relevant to imparting a pretilt angle to an orientation film using an optical orientation technique, see Japanese Patent Laid-Open No.142608/1998(literature 5).